(1) Field of the Invention
The present invention relates generally to the field of sonar and more specifically to sonar systems using inverse beamforming techniques.
(2) Description of the Prior Art
current sonar systems include many different configurations using a variety of technologies. However, because a sonar signal from a specific source may have a complex wave front which is received at different points along a hydrophone array at different times, a beamforming process must be implemented to correlate the signals received at each point in the hydrophone array. This decomposition of the acoustic field provides the basis for sonar signal detection and tracking.
Several implementations of beamforming processes exist in the prior art. Most of these implementations have been accomplished by time delaying the time series signals from each hydrophone in order to beamform the array of hydrophones. This process is referred to as a conventional time delay beamforming sonar system. However, space and weight constraints on the hardware required for implementation of a conventional time delay beamforming system limits, in practice, the number of individual beams which can be formed. Because of this limited number of beams, conventional beamforming systems must use beams which are spaced relatively far apart in azimuth. Unfortunately, such spacing may cause low intensity signals located between beams to be lost. Additionally, on these conventional sonars fixed threshold levels must be established to avoid erroneous signal declarations.